How to return a JSON object conditionally

Hi I’m working on a web App project and I have the following component that is returned by antd Menu object.

const items = [
        {
          label: <Link to='/register'>Register</Link>,
          key: 'register',
          icon: <UserAddOutlined />,
          style: { marginLeft: 1030},   // problem: hard-coded margin
        },
        {
          label: <Link to='/login'>Login</Link>,
          key: 'login',
          icon: <UserOutlined />,
          style: { marginLeft: 'auto'},
        },               
      ];

return <Menu mode="horizontal" items={items} />;

Now I have an object named user. If user is not null (which means there is a user who is logged in currently), I want to hide register in the above items object; otherwise I want to show ”’register”’ in the Menu. The Menu component will be looked like:
enter image description here

Can anyone help me with that? Thanks!